This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A068130 #8 Dec 05 2013 19:55:10 %S A068130 78,276,465,528,780,861,1176,1275,1653,1770,2346,2850,3570,3741,4371, %T A068130 4560,5253,5460,6216,6441,7260,7503,11175,12246,12561,14028,15225, %U A068130 17205,20706,22155,24090,24531,26106,28203,30381,32640,33153,35511 %N A068130 Triangular numbers with sum of digits = 15. %C A068130 1. The sequence is unbounded, as the (2*10^k +3)-th triangular number is a term. 2. The sum of the digits of triangular numbers in most cases is a triangular number. 3. Conjecture: For every triangular number T there exist infinitely many triangular numbers with sum of digits = T. %t A068130 Select[Accumulate[Range[300]],Total[IntegerDigits[#]]==15&] (* _Harvey P. Dale_, Oct 09 2012 *) %Y A068130 Cf. A068127, A068128, A068129. %K A068130 base,easy,nonn %O A068130 1,1 %A A068130 _Amarnath Murthy_, Feb 21 2002 %E A068130 More terms from _Sascha Kurz_, Mar 06 2002